地震照明分析及其在地震采集设计中的应用

Seismic illumination analysis and its applications in seismic survey design

地震照明分析是在给定地下背景结构的情况下用模拟方法研究采集系统对地下结构的探测能力.对目标照明的影响主要来自观测系统的设置,上覆地质结构的复杂性以及目标倾角等三项因素.我们将上述因素的影响统一纳入到对照明的定量计算中.本文阐述了关于地震照明的一系列基本概念,并基于波动理论给出对不同类型照明的计算方法.首先将入射和散射波分解到局部角度域并导出局部照明矩阵,它包括了在目标附近所有可能的入射和散射方向对照明的贡献.从照明矩阵出发,研究入射和反射波在角度域中与反射面的相互作用,并由此获得对地下结构的不同照明描述.作为例子,具体给出了对局部照明矩阵,空间体照明,反射面定向照明,反射面照明角度覆盖,以及对反射面可视性的计算方法,并给出了相应的数值计算结果.最后,讨论了照明分析方法在地震采集设计中的一些可能应用.

Given the subsurface background velocity,seismic illumination analysis simulates the detecting capability of a specific acquisition system to subsurface targets.Based on the wave theory,we present the basic concept and detailed algorithms for illumination analysis.To quantify the problem,all major factors affecting the illumination,i.e.,acquisition geometry,overburden structure,and the target dipping angle,are included into consideration.We start from decomposing both incident and scattering waves into local angle domain and formulating the local illumination matrix,which is composed of illumination contributions from all possible incidence/scattering directions at the target location.Based on the illumination matrix,we investigate interactions between incident/scattering waves and the target in local angle domain,and derive illuminations for various purposes,including the volumetric illumination,target oriented illumination,target illumination angle coverage,and the visibility calculation.A group of numerical examples are presented to demonstrate how illuminations are actually calculated along with their wide applications.Finally,the application of illumination analysis in seismic survey design is discussed.